The present invention relates to the handling of a tubing string in a well bore and, in particular, to a locking telescoping joint for use in a conduit connected to a wellhead which permits the conduit to be axially displaced to a new position in the well bore without disconnecting the conduit from the wellhead and secured in new positions using the locking telescoping joint.
Downhole operations and the handling of a tubing string in a completed well has always presented a certain challenge, especially when working in wells having a natural pressure.
In Applicant""s U.S. Pat. No. 5,957,198 which issued Sep. 28, 1999 and is entitled TELESCOPING JOINT FOR USE IN A CONDUIT CONNECTED TO A WELLHEAD AND ZONE ISOLATING TOOL, the specification of which is incorporated herein by reference, a telescoping joint is described for use in a conduit connected to a wellhead. The telescoping joint is adapted to support downhole well tools and to permit the downhole well tools to be axially displaced in the well bore without disconnecting the conduit from the wellhead. The telescoping joint is freely extendable and retractable. Downhole anchors or packers are used to support the conduit in the well bore. Although the telescoping joint has proven extremely useful and has generated significant commercial interest, it is not ideally suited for all downhole tasks and applications due simply to its freely extendable and retractable features. In order to extend the use of the telescoping joint into yet a broader range of applications, further improvement of the telescoping joint, particularly to enable releasably locking the telescoping joint at a selected extension, is desired.
For example, production tubing strings are generally anchored at the bottom end to the cased well bore. The length of the production tubing string is usually between 1,500 and 5,000 m (5,000xe2x80x2-16,000xe2x80x2). Over time, a production tubing string will sag under its own weight because of the significant length. This is a disadvantage if a surface driven reciprocating pump is used for production because a sucker rod used to drive the pump may wear and bind in the sagging production tubing string. In order to overcome this problem, long production tubing strings are usually tensioned before production is started. The tensioning process involves unhooking the production tubing from the tubing hanger; pulling up the production tubing string to tension it to a desired extent; marking the production tubing string where it should be reconnected to the tubing hanger; preparing a pup joint having a length equal to a distance from the mark to a next joint in the tubing string; replacing the top joint with the pup joint and re-connecting the tubing hanger. This is a time consuming and expensive procedure that may require killing the well. It is therefore desirable to provide a tool for tensioning a tubing string without removing the wellhead from the well.
There are also times when it is desirable to load a tubing string in compression. For example, if a downhole submersible pump is used for production, equipment costs can be reduced by using a less expensive compression packer to anchor the production tubing above the submersible pump. In order to ensure that the packer does not slip, it must be constantly loaded with compressive force. It is therefore desirable to provide a telescoping joint that permits a production tubing to be locked in compression.
Latch assemblies and collet devices for interconnecting tubing members are well known in the art. Examples can be shown in U.S. Pat. No. 4,391,326 entitled STINGER ASSEMBLY FOR OIL WELL TOOL which issued to Dresser Industries, Inc. on Jul. 5, 1983; U.S. Pat. No. 4,513,822 entitled ANCHOR SEAL ASSEMBLY which issued to HUGHES TOOL COMPANY on Apr. 30, 1985; U.S. Pat. No. 4,681,166 entitled INTERNAL NONROTATING TIE-NECK CONNECTOR which issued to Hughes Tool Company on Jul. 21, 1987; and U.S. Pat. No. 4,722,390 entitled ADJUSTABLE COLLET which issued to Hughes Tool Company on Feb. 2, 1988.
These patents generally describe an annular latch carried by an inner conduit having collet arms that are radially flexible and adapted to engage a latch point on an outer conduit. A relative axial movement between the two conduits is permitted in one direction only to permit threads of the collet arms to ratchet into or out of engagement with the threads of the outer conduit while the relative axial movement in an opposite direction is generally inhibited by the threaded connection to support a work load unless another manipulation is performed. However, none of these patents suggest a latch assembly to releasably lock a telescoping joint in a relative axial extension. Furthermore, these patents do not show or suggest a latch assembly having a plurality of latch points disposed along a travel length of a telescoping joint.
It is an object of the invention to provide a telescoping joint for use in a conduit connected to a wellhead to permit the conduit to be axially displaced and locked in the displaced position in the well bore without disconnecting the conduit from the wellhead.
It is another object of the invention to provide a telescoping joint for use in a tubing string in a well bore, which includes a latch assembly for locking the telescoping joint at a predetermined axial extension.
It is a further object of the invention to provide an apparatus for use in a tubing string in a well bore to maintain tension or a compression on the tubing string.
It is yet a further object of the invention to provide a method of maintaining tension or compression on a tubing string in a well bore.
In accordance. with one aspect of the invention a locking telescoping joint is provided for use in a conduit connected to a wellhead to permit the conduit to be axially displaced in the well bore without disconnecting the conduit from the wellhead. The locking telescoping joint comprises first and second telescopingly interconnected tubular sections having opposite ends adapted for connection to the conduit. A latch assembly is provided for releasably locking the first and second tubular sections in at least one position between a fully retracted and a fully extended position.
Preferably, the latch mechanism comprises a first engaging member affixed to one of the tubular sections, and at least one second engaging member affixed to the other tubular section. The first engaging member is adapted to be releasably received in the second engaging member in order to lock the telescopic tubular sections in an axial position relative to each other. The latch mechanism may be any type of releasable engagement adapted to support the weight of a tubing string. For example, a J-latch, key, collet or slip type latch mechanism may be used.
According to a first embodiment of the invention, the latch assembly includes at least one pin radially extending from one of the tubular sections and a plurality of axially spaced-apart slots defined in the other of the tubular sections. The slots are preferably interconnected by an axial groove adapted to serve as a passage route for the pin.
According to another embodiment of the invention, one of the tubular sections includes a radially collapsible collet which can be manipulated between a collapsed condition for axial movement of the telescoping joint and an expanded condition for locking the telescoping joint at a predetermined extension, and the other of the tubular sections includes at least one cooperative latch point, the cooperative latch point being adapted to cooperate with the collapsible collet during the manipulation between the collapsed and expanded conditions.
More specifically, one embodiment of the collet type latch mechanism includes a traveling collet which is adapted to be collapsed by the at least one cooperative latch point when forcibly moved past the latch point in either axial direction, and a locking collet which is adapted to be manipulated between a collapsed condition for axial movement of the telescoping joint and an expanded condition for locking the telescoping joint at a predetermined extension.
In accordance with another aspect of the invention, the telescoping joint enables a method for maintaining tension or compression on a tubing string in a cased well bore. The method comprises the steps of: a) inserting a lift rod string into the tubing string which is attached at a top end to a wellhead and anchored at a bottom end to the cased well bore, the tubing string including a locking telescoping joint in the top end; b) latching the rod to a latch point of the telescoping joint; c) retracting or extending the telescoping joint to tension or compress the tubing string by manipulating the rod; d) and, locking the telescoping joint in the retracted or extended position using a latch assembly in the telescoping joint to maintain the tension or compression on the tubing string.
The telescoping joint with the latch assembly in accordance with the invention provides improved functionality compared with the telescoping joint described in Applicant""s issued U.S. Pat. No. 5,957,198 and is adapted for use in each application described in that patent. Furthermore, the selective extension locking feature enables the use of the telescoping joint to be extended to new applications, such as the above-disclosed examples of tensioning or compressing the tubing string in a cased well bore, as well as many others. For example, the locking telescoping joint in accordance with the invention can be used to reposition or otherwise manipulate downhole tools. Such tools include any one of a zone isolation tool, a packer, a hanger, a plug, a subsurface safety valve, and a downhole tool having a slip, collet, threaded or keyed locking engagement that is releasable and resetable by remote manipulation from a surface surrounding the well. Consequently, the time and cost of well completion and well maintenance are reduced as is the cost of production of hydrocarbons in wells with a mobile oil/water interface or other condition that requires periodic downhole maintenance.